Opacification of the crystalline lens of the eye produces what is commonly referred to as a cataract. Restoration of sight is usually effected by surgical removal of the affected lens and possible replacement with an artificial intraocular lens.
In extracapsular cataract extraction, a small incision is made in a peripheral portion of the cornea or sclera. A cystotome instrument is inserted through the incision and employed to cut open the anterior wall of the capsule containing the lens. This procedure is referred to as a capsulotomy. The lens is then removed through the openings in the anterior wall and the cornea.
In a cataract extraction technique known as phacoemulsification, the lens is emulsified with an ultrasonic probe and sucked out of the eye through a passage in the probe.
These cataract extraction techniques are well known and are described and illustrated, for example, at Pages 84-91 in Cataracts by Julius Schulman, M.D., published in 1984 by Simon & Schuster, Inc. The capsulotomy there described employs a needle cystotome to make numerous cuts, resembling beer can openings, in the anterior wall of the capsule. The resulting rough edge at the opening in the anterior wall can sometimes interfere with phacoemulsification and aspiration of the lens.
U.S. Pat. No. 4,708,138, granted Nov. 24, 1987, to B. B. Pazandak for "Rotating Surgical Cutting Knife" discloses an instrument with a movable cutting blade intended to produce a smoother anterior capsulotomy.
A more recent approach to capsulotomy involves creating a continuous tear of the anterior wall to produce a smooth-edged round opening. The continuous tear capsulotomy is known as "capsulorhexis". Such a capsulotomy facilitates removal of the old lens and also facilitates in-the-bag implantation of an intraocular lens.
The present invention provides a forceps instrument which is particularly useful in performing the capsulorhexis.
United Kingdom Patent No. 113,482, dated Feb. 21, 1918, discloses "New and Improved Eye Forceps" for cataract removal. The construction of the forceps there disclosed provides for removal of not only the lens but also the entire capsule containing the lens. This is a much more traumatic operation than extracapsular extraction.
U.S. Pat. No. 3,834,021, granted Sep. 10, 1974, to R. W. White, et. al. for "Precision Instrument System" discloses a scissors-type surgical instrument which can be manipulated by one hand. The instrument would appear to have no usefulness in eye surgery.